Some shows leave you scratching your head, wondering when they went wrong. At least “Collision” makes it easy: It goes south in the first minute. And it’s all downhill from there — a better title would be “Train Wreck.”

Playwright Lyle Kessler doesn’t lack cachet: In a couple of months, a revival of his 1983 hit, “Orphans,” is coming to Broadway with Alec Baldwin and Shia LaBeouf.

Despite his “should know better” experience, Kessler’s new play, an inept tale of moral corruption on a college campus, seems to have been written by a megalomaniacal 15-year-old.

And David Fofi’s clueless production for the Amoralists company makes things even worse.

Kessler is tackling a delicate subject: A nihilistic college student casts a spell on his roommate, his girlfriend and even his philosophy professor, and eventually drives them to a gun-fueled rampage.

We’re meant to see just how cunning Grange (James Kautz) is when he talks his new roommate, the nerdy Bromley (Nick Lawson), into giving up the better bed in their spartan dorm. Next thing we know, the evil mastermind has plastered the walls with posters of Che Guevara, Janis Joplin and Kurt Cobain. This guy is supposed to be cool?!

The next logical step is to buy guns from Renel (Craig “muMs” Grant), the rare arms dealer who takes personal checks, makes house calls to campuses and still speaks like an escapee from “Shaft.”

“I need a private jet an’ ladies galore an’ I need a truck full of huge uncut African diamonds, and I need a mother’s love!” Renel tells his client.

And what we need is for something, anything, to make a shred of sense. For starters, it would help if the grim Kautz weren’t a good 10 years too old to play an undergrad, and if he showed at least a smidgen of the dark charisma a leader requires.

At times, the show is so inadvertently laughable that, well, you just have to laugh, as when Doe earnestly explains that her musician dad called her Do Re Mi.